The Key Algorithm Research Of Beidou Satellite Signal Acquisition

With the development of the Beidou navigation system which is independently developed by China,the research on navigation receivers is also rapidly developing.However,at present,navigation receivers still have many technical difficulties,and there is no breakthrough in progress.This has caused tremendous influence on the Beidou navigation system application.Therefore,it is urgent to improve the performance of receivers.According to the function,the receivers can mainly divides into three parts,the front-end RF,base band digital signal processing and navigation and positioning,the current research hot spots is base band signal processing,which contain the acquisition and tracking.The acquisition is the first step of base band signal processing and its performance directly affects the precision and speed of the follow-up tracking,therefore,it is particularly important to carry out in-depth research on signal acquisition to improve the performance of the acquisition.This paper mainly research on signal acquisition,and improve the existing algorithms to shorten the time of acquisition and improve the efficiency of the acquisition.At the beginning of the Beidou signal design,in order to improve the correlation between the satellite signals and improve the anti-interference ability of the narrow band,the main code is used to modulate the signal with two times encoding.However,because the two time encoding may cause a bit turnover,the capture peak can be reduced and the signal can not be captured effectively.At the same time,in the signal sampling process,the signal cannot be effectively captured.Following the traditional Nyquist sampling theorem,the sampling rate is high and the amount of data is large,which seriously affects the performance of the receiver.And two kinds of acquisition algorithms are proposed for the problem of high complexity.(1)The novel FFT parallel acquisition algorithm.First,the algorithm assumes that there is no transition,and the traditional method is used to complete relevant operation on the receiving signal and local signal to obtain the results.Then it improves the reception signal and local signal,and performs the correlation operation.Finally,the results of the two related operations are obtained,and the maximum correlation peak is obtained.This algorithm solved the problem that the coherent accumulation peak reduced caused by bit transition.In addition,the Fast Fourier Transform(FFT)is used to further reduce the overall calculation.(2)Acquisition algorithm based on compressed sensing.Satellite signal acquisition process needs certain hardware resources,and time consuming,in order to save hardware resources,reduce the cost,at the same time in order to improve the anti-noise performance of reconstruction algorithm and remove the measurement noise,the paper puts forward a kind of compressed sensing satellite signal acquisition algorithm based on Kalman filtering.Firstly,the sparsity of Beidou satellite signals is analyzed,the sparse transformation matrix is constructed and the observation matrix is selected for observation.Secondly,Kalman filtering is introduced in signal reconstruction,and the best signal estimation is obtained in each iteration,and the effective information is filtered by weak matching,and redundant information is eliminated to reconstruct the signal.Finally the accurate estimation of the code phase and frequency is obtained.The experimental carry out from computational complexity,integral time,anti noise performance and acquisition performance.The results show that the proposed algorithms are improved compared to traditional algorithm,so can effectively be used to acquisition process.